Researchers have found DNA segment associated with severity of autism symptoms

University of Colorado researchers have found a segment of DNA — in the same gene family that appears to have helped the human brain become larger and more complex than in any other animal’s — that might also be linked to the severity of autism.

The gene family consists of more than 270 copies of a DNA segment called DUF1220, which codes for a protein domain (a specific functionally important segment of a protein). The more copies of a specific DUF1220 subtype a person with autism has, the more severe the symptoms — communicative impairments, social deficits and repetitive behaviors, according to a press release on a paper published in the PLoS Genetics.

This link of increasing severity of autism to increasing copies (dosage) of a gene-coding segment of DNA is a first, and it suggests a focus for future research into the condition Autism Spectrum Disorder (ASD), according to the CU press release.

One federal study showed that the ASD affects one in 88 children.

“Previously, we linked increasing DUF1220 dosage with the evolutionary expansion of the human brain,” said biochemistry and molecular genetics professor James Sikela with the CU School of Medicine. “One of the most well-established characteristics of autism is an abnormally rapid brain growth that occurs over the first few years of life. That feature fits very well with our previous work linking more copies of DUF1220 with increasing brain size. This suggests that more copies of DUF1220 may be helpful in certain situations but harmful in others.”

The research by Sikela, Jack Davis, PhD., and colleagues examined the presence of DUF1220 in 170 people with autism. They looked at only one of six different types of subsets of DUF1220 in this study and said they plan to study others that might play a role in ASD.

Davis, who contributed to the research while a postdoctoral fellow in Sikela’s lab, has a son with autism and a very personal motivation to seek out the genetic factors that cause it, the press release said.

What is striking, Davis said, is that DUF1220 is as common in people without ASD as in people who do. So the link of dosage to symptom severity is only found in people who have the disorder.

“Something else is at work here, a contributing factor that is needed for ASD to manifest itself,” Davis said.

Electa Draper is the health writer for The Denver Post and has covered every news beat in a 22-year journalism career at three newspapers. She has a bachelor's degree in biology and a master's in journalism.